Large portable lathes generally include a drive assembly (normally called a headstock) to rotate a workpiece along with two bearing pedestals which support the workpiece while it is being turned. There is a large drive shaft which transmits the power from the headstock to the workpiece, and it is used to take up any misalignment between the center of rotation of the headstock and the workpiece. However, it is a difficult task to attach the drive shaft between the headstock and the workpiece because the workpiece is usually large and heavy. Consequently, a crane is typically required to move the workpiece axially while at the same time, the headstock drive shaft is rotated until all of the bolt holes on the drive shaft and workpiece can be lined up and tightened.
The present invention provides a drive shaft that can be extended or retracted, with opposite ends able to swivel with respect to each other, thereby facilitating set-up of the lathe and workpiece.
In accordance with an exemplary embodiment of the invention, the drive shaft is comprised of two separate shaft pieces, each containing a standard universal joint at opposite ends thereof. One shaft piece slides into the other in telescoping fashion, which allows for the axial adjustment of the drive shaft. At the same time, one shaft piece is rotatable relative to the other, thereby also providing great flexibility, especially considering the use of universal joints at the end of each shaft. Once positioned where desired, the shaft pieces are locked in place relative to each other via a conventional circumferential friction locking device which allows it to transfer the torque and horsepower of the input drive mechanism.
Accordingly, in its broader aspects, the present invention relates to a drive shaft assembly for a portable lathe connectable between a workpiece and a lathe headstock, the drive shaft assembly comprising a first hollow shaft; a second shaft axially aligned with and telescopingly received in the first shaft, for permitting an effective axial length of the drive shaft assembly to be altered within a limited range; the first and second shafts also being rotatable relative to each other; opposite ends of the first and second shafts having mounting flanges attached thereto; and a locking device effective to lock both first and second shafts relative to each other.
Other objects and advantages of the subject invention will become apparent from the detailed description which follows.